Gellable binders

ABSTRACT

The invention concerns the binding of refractory powders into self-supporting &#39;green&#39; shapes which are fired to provide refractory objects. In accordance with the invention the binders are based on zirconium salts and include a separate gell time delaying agent to ensure satisfactory gelling and to achieve control and to allow complex shapes to be made.

This invention relates to the manufacture of refractory articles. More specifically the invention relates to a manufacturing process wherein a flowable liquid slurry of a refractory powder dispersed in a liquid binder is prepared and poured into an appropriate shaped mould and allowed to set by gellation of the binder. The set moulded shape, referred to as the `green` shape, is then removed from the mould and fired into a sintered refractory mass.

For such a purpose to be commercially successful the following parameters have to be satisfied:

1. The binder and the refractory particles must be capable of producing a slurry which is sufficiently fluid to fill a complex mould.

2. The gelling time of slurry should, preferably, be controllable. Thus to produce a simple shape such as a rectangular block the moulding operation can be carried out rapidly and, in order to achieve an economically viable process when a single mould is used, the setting of the binder should be caused to take place as rapidly as possible. In the case of a complex shape, such as a burner part, however, filling and handling of the mould is a slower operation and the gellation should be correspondingly delayed.

3. The `green` shape should have reasonable strength to allow a complex shape to be removed from the mould and transported to a drying oven and then to a firing furnace. The breakage of a green shape wastes valuable material, the setting of the binder being an irreversible process, and time.

4. After firing the binder should leave a matrix which effectively binds the refractory particles together.

5. After firing the binder should leave only highly refractory residues to constitute the matrix.

In the past binders derived from organic silicates which hydrolyse under appropriate conditions to give silicic acid have been widely used. Silicic acid gels to set the slurry and after firing leaves silica as the refractory matrix holding the refractory grains together. Silica is a refractory oxide and is recognised as such, but its refractory properties do not compare favourably with the refractory properties of, for example, alumina and zirconia. Additionally, ethyl silicate being manufactured from ethyl alcohol, which is a petroleum-derived product, is becoming increasingly expensive.

It is an objective of the present invention to provide a binder for refractory powders such binder being based on zirconium compounds which binder after firing leave a highly refractory residue of zirconia as the principal constituent refractory matrix.

U.S. Patent Specification No. 979,197 of the Zirconium Corporation of America relates to a refractory cement consisting of a dry matrix of refractory powders, binder and gelling agent which when wet and worked into a viscous self-supporting consistency can be `trowelled` into moulds to form simple shapes. Group IVB organic salts such as zirconium acetate are suggested as binders. The parameters set out above are not necessary as, at cement consistencies, control of gellation is not significent as the cement in itself is sufficiently coherent to form a rigid shape. The compositions referred to in this specification are not liquid flowable slurries capable of being poured into and filling the cavities of complex moulds.

U.S.A. Pat. Specification No. 3,203,812 of Unilever Limited, relates to organic zirconium esters which are covalent complexes and have to be dissolved in expensive and inconvenient organic solvents such as carbon tetrachloride. The techniques of this Patent Specification are costly and complex.

According to the present invention there is provided a method of making refractory articles such method comprising the steps of:-

(a) preparing a liquid binder by mixing an aqueous solution of a zirconium salt with a gellation-inducing agent selected from the group consisting of the amino alcohols, morpholine, dead burned magnesia powder and powdered magnesia-containing spinels, when the zirconium salt is acid and the dead burned magnesia powder and powdered magnesia-containing spinels only when the zirconium salt is basic and with a gellation-delaying agent selected from the group consisting of magnesium salts, ammonium lactate, ammonium chloride compounds which in solution form dipolar (Zwitter) ions, monosaccharides and the polyhydric alcohols, triethanolamine hydrochloride and acetic acid being additional to the last mentioned group when the gellation-inducing agent is triethanolamine, and alkali metal borates being additional to the last mentioned group when the gell-inducing agent is the dead burned magnesia or powdered magnesia containing spinel.

(b) mixing a refractory powder with the liquid binder and forming a liquid flowable slurry.

(c) pouring the slurry into a mould to fill the cavities of the latter. (d) allowing the slurry in the mould to set to a coherent green shape.

(e) drying and firing the green shape into a sintered refractory mass.

The terms `heavy and light` in calcined magnesia powder refer to bulk density and particle size. Thus `heavy` calcined magnesia powder has relatively large grains and relatively high bulk density. `Light` calcined magnesia has relatively small particles and a relatively low bulk density. Typically 20 g light calcined magnesia will occupy a volume of not less than 150 cc. Light calcined magnesia powder is preferred in the methods of the present invention wherein a separate gell controlling agent is used. The calcining operation carries out on the magnesia is preferably of short duration and to obtain a lightly calcined magnesia calcination is carried out typically between 600° and 900° C. This is in contrast to the `dead burning` procedure wherein temperatures over 900° C. are used. In general terms `dead burned` magnesia is less soluble in acids than `calcined` magnesia. For a more detailed treatment reference is made to the 26th Extra Pharmacoepia 1972, page 137.

Suitable aqueous solutions of the zirconium salt include aqueous solutions of zirconium acetate, zirconium oxychloride, zirconium formate (all acidic) and ammonium zirconium carbonate (basic).

Although any refractory powder may be used the system is especially suitable for use with zircon and zirconia also magnesia and other basic refractories, such as chrome magnesite systems. The system of the invention can also be used to bind acidic or neutral refractories such as alumina and silicon carbide. The fusion product of zircon sand and alumina is a suitable refractory aggregate.

The invention will now be further illustrated in the following Examples. The term `gel` used hereinafter unless otherwise qualified signifies a coherent gel which will bind a powdered refractory:

Examples of the Use of Aminoalcohols as Gell-inducing Agents for Zirconium Acetate Solution. Example I Diethanolamine as Gell Inducing Agent

The gelation agent was a solution of one volume of diethanolamine in one volume of water. This is solution A.

with 10.0 g magnesium acetate crystals (4H₂ O) (gell time controlling agent) in 50 ml zirconium acetate solution, 10 ml of this solution+ 3.0 ml solution A-- gel in 20 seconds, strength improving on standing 10 ml of this solution+ 2.5 ml solution A-- a weak gel in 1 minute

with 15.0 magnesium acetate crystals (4H₂ O) in 50 ml zirconium acetate solution 10 ml of this solution+ 3.0 solution A-- good gel in 20 seconds 10 ml of this solution+ 2.5 ml solution A-- good gel in 20 seconds Diluted solution A by adding 1 volume of water to 1 volume of solution A, giving solution B 10 ml of Magnesium acetate/zirconium acetate solution+ 5 ml solution B-- good gel in 20 seconds pH 8.5 10 ml of Magnesium acetate/zirconium acetate solution+ 4.5 ml solution B-- no gel in 20 minutes pH 7.0

Example II Triethanolamine as Gel Inducing Agent

The gelation agent was a solution of one volume of triethanolamine in one volume of water. This is solution C. with 10 g magnesium acetate crystals (4H₂ O) (gel time controlling agent) in 50 ml zirconium acetate solution.

Using 10 ml of this solution, with given volumes of solution C 3 ml-- pH 6 3.5 ml-- pH 7 4.0 ml-- pH between 7 and 7.5, rubber like gel in 2 minutes 4.5 ml-- pH 7.5, rubber like gel in 30 seconds All pH determinations were made by using B.D.H. Universal Indicator solution. (Supplied by B.D.H. Chemicals Ltd., Poole.)

with 15 g magnesium acetate crystals (4H₂ O) in 50 ml zirconium acetate solution. Using 10 ml of this solution with 4.0 ml of solution C-- gel in 2 minutes, a rubbery gel.

with 5 g magnesium acetate crystals (4H₂ O) in 50 ml zirconium acetate solution. Using 10 ml of this solution with 4.0 ml solution C-- in 1 minute 15 seconds-- gel now very flexible and rubbery. 10 ml zirconium acetate solution, NO magnesium acetate crystals dissolved

with 4.0 ml solution C-- localised gelation, not a coherent gel. Conclude that magnesium acetate lengthens the gel time, also strengthens the gel.

Example III Triethanolamine/acetic Acid Experiments

Dissolved 30 g triethanolamine in 30 ml water and added 12 g glacial acetic acid. This solution would not gel zirconium acetate solution. Needed 60 g triethanolamine to obtain a gel. The gel inducing solution (accelerator solution) used was made by dissolving 60 g triethanolamine in 30 ml water and adding 12 g glacial acetic acid.

10 ml zirconium acetate solution with 6 ml accelerator solution, gel in 4 minutes, good strength development on standing. with 10 g Magnesium acetate crystals (4H₂ O) (gel controlling agent

in 50 ml zirconium acetate solution. Using 10 ml of this solution with 6 ml accelerator solution, gel in 31/2 minutes, a good gel. At this stage added a further 10 g triethanolamine to the accelerator solution. 6 ml of the new accelerator solution with 10 ml zirconium acetate solution gave a good gel in about 1 minute. 6 ml of the new accelerator solution with 10 ml of solution of magnesium acetate crystals (4H₂ O) in 50 ml zirconium acetate solution gave a good gel in 31/2 minutes. Again note lengthening of gel time by magnesium acetate.

Examples Demonstrating Use of the Zirconium Acetate/Magnesium Acetate/Triethanolamine System in the Preparation of Shaped Refractory objects. Example IV

A crucible was prepared by mixing 27 ml of a solution of magnesium acetate in zirconium acetate solution obtained by dissolving 20 g magnesium acetate crystals in 100 ml acetate solution (ZrO₂ 22%w/w), with 12 ml of a 50% aqueous solution of triethanolamine, then adding 200 g powdered Sillimanite mix. The resulting slurry was poured into the mould and allowed to set. After 10 minutes, the crucible was removed from the mould, air-dried and then fired at 1550° C. The fine sillimanite mix used in this Example and hereinafter was

    ______________________________________                                         Molochite - 16 + 30 grade                                                      2 parts by weight                                                              P.B. Sillimanite 100 CML grade                                                 12/3 parts by weight                                                           Fused alumina - 100 B.S. 410                                                   1/3 part by weight                                                             ______________________________________                                    

Example V

An element carrier was prepared by mixing in the order

27 ml solution of magnesium acetate in zirconium acetate (composition 10 g magnesium acetate (4H₂ O) crystals dissolved in 100 ml zirconium acetate solution) 12 ml 50% aqueous solution of triethanolamine 400 g of a mixture of zircon and zirconia powders.

The resulting slurry was poured into the mould, which was vibrated. After 5 minutes, when the slurry had hardened, the carrier was removed from the mould, air-dried and fired at 1550° C.

Example VI

A crucible was prepared by mixing 17.5 ml solution of magnesium acetate in zirconium acetate (composition as in Example IV) with 7.5 ml 50% aqueous solution of triethanolamine, then adding 200 g fused alumina mix. The resulting slurry was poured into the mould, which was vibrated. When the slurry had hardened (after approximately 5 minutes) the crucible was removed from the mould, air-dried and fired at 1550° C. The fused alumina mix comprised

    ______________________________________                                                 3/16 + 1/8                                                                     7%                                                                             1/8  + 1/16                                                                    23%                                                                            1/16 + 22                                                                      30%                                                                              - 100                                                                        40%                                                                    ______________________________________                                    

Percentages are by weight and the screen sizes are B.S. 410 sieves.

Basic Refractory Aggregates-- Use of Magnesium Acetate to Control Setting Time of Slurry. Example VII

Slurries were prepared by mixing 20 ml of the magnesium acetate-- zirconium acetate solution with 100 g of powdered basic refractory aggregate and the setting time of the slurry noted. The magnesium acetate-- zirconium acetate solution was prepared by dissolving a given weight of magnesium acetate crystals (CH₃.COO)₂ Mg.4H₂ O in 100 ml of zirconium acetate solution (containing approx. 22% w/w Zro₂). The powdered basic refractory aggregate consisted of 2 parts by weight of Steetley ceramic powder MCH45 and 1 part by weight of Steetley ceramic powder MCH200. The table gives the results obtained.

    ______________________________________                                         Wgt of magnesium acetate crystals                                              (gms) dissolved in 100ml                                                                               Setting time                                           of zirconium acetate solution                                                                          of slurry                                              ______________________________________                                          0                      21/2 min                                               10                      33/4 min                                               20                      43/4 min                                               30                      61/4 min                                               40                      11  min                                                ______________________________________                                    

It will be noted that increasing the proportion of gell time controlling agent increases the gelling time. The Steetley ceramic powders are synthetic spinels prepared by sintering a mixture of magnesia and chrome ore. A typical chemical analysis is

    ______________________________________                                         Chrome oxide     24% as Cr.sub.2 O.sub.3                                       Magnesium oxide  41% as MgO                                                    Iron oxides      12% as Fe.sub.2 O.sub.3                                       Aluminium oxide  20% as Al.sub.2 O.sub.3                                       Silicon oxide     2% as SiO.sub.2                                              Calcium oxide     1% as CaO                                                    Specific gravity 3.85                                                          ______________________________________                                    

Examples Demonstrating the Use of the Zirconium Acetate/Magnesium Acetate System in the Preparation of Shaped Refractory Objects from Basic Refractory Powders. Example VIII

A shaped refractory, suitable for use as an electric element carrier in electric furnaces, was prepared by mixing 45 ml of a solution of magnesim acetate in zirconium acetate (obtained by dissolving 10 g magnesium acetate crystals in 100 ml zirconium acetate solution) with 300 g of a powder comprising equal parts by weight of Steetley Ceramic Powders MCH45 and MCH200. The resulting slurry was poured into the mould and allowed to set. When the slurry had hardened, after approximately 2 minutes, the carrier was removed from the mould, air-dried and fired at 1550° C. Example IX

A crucible was prepared using magnesia supplied by Dynamit Nobel (U.K.) Limited. The quantities of components used were as follows

35 ml solution of magnesium acetate in zirconium acetate (composition as in Example VIII)

200 g magnesia mix comprising: 2 parts by weight fused magnesia -8+ 30 mesh 1 part by weight fused magnesia -240 mesh

The resulting slurry was poured into the mould and allowed to set. After 3 minutes, the crucible was removed from the mould, air-dried and fired at 1550° C.

Example X

A crucible was prepared by mixing 25 ml solution of magnesium acetate in zirconium acetate (composition as in Example 13) with 200 g B40 refractory grain (A. P. Green Co., Mexico, Missouri, U.S.A.). The resulting slurry was poured into a suitable mould which was being vibrated and allowed to set. After 2 minutes, the object was removed from the mould, then air-dried and fired at 1550° C. to give a crucible.

Example XI

Attempts to gel zirconium acetate solution with aqueous solutions of ethanolamine, diethanolamine and triethanolamine in the absence of a gel time controlling agent proved unsatisfactory, localised gellation being observed in all cases. If, however, a sufficient quantity of a gel time controlling agent magnesium acetate (CH₃ COO)₂ Mg 4H₂ O is dissolved in the zirconium acetate solution it is possible to obtain good coherent gels which develop considerable strength on standing.

The following table gives results obtained using magnesium acetate.

    __________________________________________________________________________     Mg acetate / Zr acetate / organic base system                                                                              Vol                                                                            acetate                                                            % ethylene                                                                           Vol   solution                           % ethanolamine                                                                         % triethanolamine                                                                       % water                                                                             % 640P                                                                              % 740P                                                                              glycol                                                                               (ml)  (ml) T gel                         __________________________________________________________________________     50      --       --   50   --   --    1.5                                                                               10      localised gel                 30      --       --   70   --   --    2.5                                                                               10      localised gel                 --      70       --   30   --   --    3  10      no gel                        --      "        --   "    --   --    4  10      21/4 mins                     --      "        --   "    --   --    5  10      11/4 mins                     --      50       50   --   --   --    3.5                                                                               10      no gel                        --      "        "    --   --   --    4  10      31/2 mins                     --      "        "    --   --   --    5  10      55 secs                       --      50       --   50   --   --    4  10      no gel                        --      "        --   "    --   --    5  10      6 mins                        --      "        --   "    --   --    6  10      31/4 mins                     --      50       --   --   50   --    4  10      25 mins                       --      "        --   --   "    --    5  10      33/4 mins                     --      "        --   --   "    --    6  10      3 mins                        --      50       --   --   --   50    4  10      no gel                        --      "        --   --   --   "     5  10      4 mins                        --      "        --   --   --   "     6  10      3 mins                        The above Results obtained using 10 g Mg acetate / 50 ml Zr acetate            solution                                                                       --      50       50   --   --   --    3.5                                                                               10      no gel                        --      "        "    --   --   --    4  10      41/2 mins                     --      "        "    --   --   --    5  10      11/2 mins                     The above Results obtained using 15 g Mg acetate / 50 ml Zr acetate            solution                                                                       __________________________________________________________________________

    __________________________________________________________________________     Results obtained using 20 mg acetate / 50 ml Zr acetate solution                                                       Vol                                                                        Vol acetate                                                                    accel.                                                                             solution                               % ethanolamine                                                                         % diethanolamine                                                                        % triethanolamine                                                                       % water                                                                             % 640P                                                                              (ml)                                                                               (ml) T gel                             __________________________________________________________________________     30      --       --       --   70   2   10   no gel                            "       --       --       --   "    2.5 10   21/2 mins                         --      50       --       --   50   2.5 10   11 mins                           --      "        --       --   "    3.0 10   23/4 mins                         --      "        --       --   "    3.5 10   21/4 mins                         --      --       50       50   --   3   10   no gel                            --      --       "        "    --   4   10   8 mins                            --      --       "        "    --   5   10   2.5 mins                          --      --       "        "    --   6   10   11/4 mins                         --      --       50       --   50   4   10   no gel                            --      --       "        --   "    5   10   36 mins                           --      --       "        --   "    6   10   30 mins                           --      --       "        --   "    7   10   30 mins                           --      --       50       25   25   4   10   45 mins                           --      --       "        "    "    5   10   12 mins                           --      --       "        "    "    6   10   10 mins                           __________________________________________________________________________     These Results obtained using 25 g Mg acetate / 50 ml Zr acetate solution                                               Vol                                                                        vol acetate                                                                    accel.                                                                             solution                                                % triethanolamine                                                                       % water   (ml)                                                                               (ml) T gel                             __________________________________________________________________________                      50       50        4   10   21 mins                                            "        "         5   10   6 mins                                             "        "         6   10   4 mins                                             "        "         7   10   41/2 mins                         __________________________________________________________________________

Use of the Magnesium Acetate/Zirconium Acetate/Organic Base System as a Refractory Binder Example XII

The above data suggest the possibility of using the magnesium acetate/zirconium acetate/organic base system to prepare refractory objects, based on a fine sillimanite mix, for example, and the above system. A slurry was prepared by mixing 200 g sillimanite mix with the necessary quantity of binder and the time required for the slurry to set was noted. (Tgel). Results obtained using 40 g magnesium acetate/100 ml zirconium acetate solution.

    ______________________________________                                         Composition of accelerator                                                                                       Volume                                       %                           Vol. of                                                                              acetate                                      diethano-                                                                              % triethano-                                                                               %       accel.                                                                               solution                                                                              T gel                                 lamine  lamine      water   (ml)  (ml)   (mins)                                ______________________________________                                         50      --          50      10    33     3                                     50      --          50       9    34     8                                     50      --          50       8    34     90                                    --      50          50      13    26     10                                    --      50          50      15    24     7                                     --      50          50      16    23     7                                     --      50          50      18    21     8                                     Results obtained using 20 g magnesium acetate/100ml                            zirconium acetate solution                                                     Composition of accelerator                                                                        Volume    Volume                                                               accele-   acetate                                           % triethano-       rator     solution                                          lamine   % water   (ml)      (ml)    T gel                                     ______________________________________                                         50       50        11        28      10 mins                                   50       50        12        27       2 mins                                   50       50        13        26       2 mins                                   50       50        16        23      11/2 mins                                 Results obtained using 10g magnesium acetate/100ml                             zirconium acetate solution                                                     Composition of accelerator                                                                        Volume    Volume                                                               accele-   acetate                                           % triethano-       rator     solution                                          lamine   % water   (ml)      (ml)    T gel                                     ______________________________________                                         50       50        11        28      slurry did                                                                     not set                                   50       50        13        26      1 min                                     ______________________________________                                    

Preparation of Refractory Objects Based on Sintered Mullite Example XIII

In each case, a slurry was obtained by mixing 200 g Sintered Mullite (preparation of this is described by Sargeant, Isherwood & Atthis, Refractories Jnl. June 1973, p.p. 12- 18.) with the necessary amount of binder and the setting time of the slurry (Tgel) was noted)

Results obtained using 40 g Magnesium acetate (gel time controlling agent)/100 ml zirconium acetate solution.

    ______________________________________                                         Composition of accelerator (gellation inducing agent)                                                          Vol.                                                                    Vol.   acetate                                        % ethano-                                                                              % trietha-                                                                              %       accel. solution                                       lamine  nolamine water   (ml)   (ml)    T gel                                  ______________________________________                                         30      --       70      7      30      slurry                                                                         did not                                                                        set                                    30      --       70      10     30      1 min.                                 15      --       85      7      30      slurry                                                                         did not                                                                        set                                    15      --       85      9      30      30 secs.                               --      50       50      13     26      20 mins.                               --      50       50      20     20      slurry                                                                         did not                                                                        set                                    ______________________________________                                    

Effect of Ammonium Chloride (Gel Time Controlling Agent) on the Magnesium Acetate (Gel Time Controlling Agent)/Zirconium Acetate/Triethanolamine (Gel Inducing Agent) System Example XIV

Solutions of ammonium chloride in triethanolamine were used to gel zirconium acetate solution containing magnesium acetate.

    ______________________________________                                         Composition of accelerator                                                                               Volume Volume                                                                  accele-                                                                               acetate                                       % trietha-                                                                            %       % ammonium rator  solution                                      nolamine                                                                              water   chloride   (ml)   (ml)   T gel                                  ______________________________________                                         50     50      10         6      10     7 mins                                 50     50      10         8      10     7 mins                                 50     50      10         10     10     11 mins                                50     50      5          5      10     6 mins                                                           6      10     31/4 mins                                                        8      10     31/4 mins                              ______________________________________                                    

Above results obtained with 40 g magnesium acetate/100 ml zirconium acetate solution.

The following examples illustrate systems which are practical on a commercial scale. The formulation Zetabond 10 referred to is proprietary to Zirconal Processes Limited and comprises 100 ml of zirconium acetate solution (ZrO₂ content 22% w/w) in which are dissolved 10 gm of magnesium acetate 4H₂ O crystals.

Use of Zirconium Acetate Solution for Binding Refractory Powder. Example XV

Zetabond 10/640P industrial methylated spirits solution gelled by the addition of triethanolamine/triethanolamine hydrochloride solution.

(a) A cylinder was prepared by mixing 30 ml of a solution containing 60 mls zetabond 10 in 40 mls of 640P industrial methylated spirits (Zetabond 10/640P solution (60:40) with 9 ml triethanolamine hydrochloride/triethanolamine solution obtained by dissolving 5 g triethanolamine hydrochloride in 100 ml of a 40% aqueous solution of triethanolamine, then adding 200 fine sillimanite mix. The resulting slurry developed strength quite slowly. The observed setting time was 12 mins. (Time to gel in the absence of powder was 21/2 minutes.

(b) A cylinder was prepared by mixing 26 ml of a zetabond 10/640P solution (60:40) with 14 ml of triethanolamine hydrochloride/triethanolamine solution obtained by dissolving 10 g triethanolamine hydrochloride in 100 ml of a 40% aqueous solution of triethanolamine, then adding 200 g fine sillimanite mix. The slurry obtained became somewhat immobile after 3 mins. and a setting time of approximately 12 mins. was observed.

(c) A cylinder was prepared by mixing 26 ml of a zetabond 10/640P solution (80:20) with 14 ml of triethanolamine hydrochloride/triethanolamine solution obtained by dissolving 10 g triethanolamine hydrochloride in 100 ml of a 40% aqueous solution of triethanolamine, then adding 200 g fine sillimanite mix. The resulting slurry would not flow under vibration after 2 mins. The shaped object could be removed from the mould after 6 mins. but was still a little soft. (Tgel= 1 min.)

Example XVI Zetabond 10/640P Solution Gelled by Addition of Tri(Hydroxymethyl) Methylamine ("Tris") Solution.

A cylinder was prepared by mixing 26 ml zetabond 10/640P industrial methylated spirits solution (80:20) with 13 ml 50% aqueous solution of TM, then adding 200 g sillimanite mix. After 25 mins. the cylinder was firm enough to be stripped from the mould. (Tgel= 5 mins.)

Example XVII Fructose - Magnesium Chloride - Zirconium Acetate Solution Gelled by Addition of Morpholine Solution.

A cylinder was prepared by mixing 27.5 ml of a solution obtained by dissolving 12 g fructose and 8 g magnesium chloride (hydrated) in 100 ml zirconium acetate solution with 16.5 ml 50% aqueous solution of morpholine, then adding 200 g sillimanite mix. Slurry flowed quite well under vibration. Cylinder could be stripped from the mould after 5 mins. (Tgel= 21/4 mins.)

Example XVIII Fructose - Magnesium Chloride (Gel Time Controlling Agents) Zirconium Acetate Solution Gelled by Addition of Diethanolamine Solution.

A cylinder was prepared by mixing 26 ml of a solution obtained by dissolving 10 g fructose and 10 g magnesium chloride (hydrated) in 100 ml zirconium acetate solution with 13 ml 50% aqueous solution of diethanolamine, then adding 200 g sillimanite mix. The resulting slurry flowed satisfactorily under vibration. Cylinder was stripped from mould after 12 mins. (Tgel= 21/2 mins.)

Example XIX Fructose (Gel Time Controlling Agent) Zirconium Acetate Solution Gelled by Addition of Morpholine (Gellation Inducing Agent) Solution.

A cylinder was prepared by mixing 25 ml solution of 15 g fructose in 100 ml zirconium acetate solution with 15 ml 50% aqueous morpholine solution, then adding 200 g sillimanite mix. Slurry had reasonable flow properties. Cylinder could be stripped from mould after 12 mins. (Tgel= 31/2 mins.)

Example XX Fructose - Magnesium Chloride - Zirconium Acetate Solution Gelled by Addition of Ethanolamine Solution.

A tile was prepared by mixing in the order

200 ml solution of 10 g fructose and 10 g magnesium chloride (hydrated) in 100 ml zirconium acetate solution

80 ml solution comprising equal volumes of 640P I.M.S. water and ethanolamine

1500 g sillimanite mix.

The slurry remained mobile for approximately 3 mins. Tile stripped satisfactorily at 40 mins, but was rather flexible.

Example XXI Ammonium Lactate (Gel Time Controlling Agent) Zirconium Acetate Solution Gelled by the Addition of Diethanolamine Solution.

A cylinder was prepared by mixing 26 ml zirconium acetate ammonium lactate solution (80:20) with 13 ml 50% aqueous solution of diethanolamine, then adding 200 g of a fine sillimanite mix. Slurry remained mobile for approximately 7 mins. Article was stripped at 50 mins. although still a little soft.

    __________________________________________________________________________     Experiments with triethanolamine hydrochloride (gel time                       controlling agent) / triethanolamine solutions.                                __________________________________________________________________________     (a) Gellation of zirconium acetate solution.                                     TEA - Triethanolamine                                                          TEA HCl - Triethanolamine Hydrochloride                                                 Composition of                                                      Composition of binder                                                                     gelling agent                                                       % by volume        Wt.     Volume                                              zirconium                                                                             % by                                                                               % by                                                                               % by                                                                               TEA                                                                               Volume                                                                              gelling                                             acetate                                                                               volume                                                                             volume                                                                             volume                                                                             HCl                                                                               binder                                                                              agent                                               solution                                                                              64OP                                                                               TEA water                                                                              (gm)                                                                              (ml) (ml) T gel                                          __________________________________________________________________________     100    --  50  50  5  10   3    no gel                                         "      --  "   "   "  10   4    50 secs                                        "      --  "   "   "  10   6    spontan-                                                                       eous gel                                       100    --  30  70  5  10   5    no gel                                         "      --  "   "   "  10   6    no gel                                         "      --  "   "   "  10   7    50 secs                                        100    --  40  60  5  10   4    no gel                                         "      --  "   "   "  10   5    60 secs                                        100    --  30  70  21/2                                                                              10   6    no gel                                         "      --  "   "   "  10   7    35 secs                                        100    --  40  60  10 10   5    >30 mins                                       "      --  "   "   "  10   6    15 secs                                        60     40  50  50  21/2                                                                              10   4    35 secs                                        "      "   "   "   "  10   5    35 secs                                        60     40  50  50  5  10   5    45 secs                                        "      "   "   "   "  10   6    65 secs                                        60     40  40  60  10 10   4    20 secs                                        "      "   "   "   "  10   5    15 secs                                        "      "   "   "   "  10   6    15 secs                                         Experiments with triethanolamine hydrochloride/triethanolamine                solutions                                                                      (b) Gellation of zetabond 10                                                              Composition of                                                      Composition of binder                                                                     gelling agent                                                                  % by                                                                               % by                                                                               Wt.     Volume                                                     % by                                                                               vol-                                                                               vol-                                                                               TEA                                                                               Volume                                                                              gelling                                             % by volume                                                                           volume                                                                             ume ume HCl                                                                               binder                                                                              agent                                               zetabond 10                                                                           64OP                                                                               TEA water                                                                              (gm)                                                                              (ml) (ml) T gel                                          __________________________________________________________________________     100    --  40  60   5 10   5    5 mins                                         "      --  "   "   "  10   6    30 secs                                        100    --  40  60  10 10   5    7 mins                                         "      --  "   "   "  10   6    45 secs                                        80     20  40  60  10 10   4    7 mins                                         "      "   "   "   "  10   5    13/4 mins                                      "      "   "   "   "  10   6    1 min                                          60     40  40  60   5 10   3    21/2 mins                                      "      "   "   "   "  10   4    45 secs                                        "      "   "   "   "  10   5    30 secs                                        60     40  40  60  10 10   3    >20 mins                                       "      "   "   "   "  10   4    23/4 mins                                      "      "   "   "   "  10   5    2 mins                                         60     40  50  50  10 10   4    70 secs                                        "      "   "   "   "  10   5    70 secs                                        __________________________________________________________________________      Note: similar results cannot be obtained by dosing triethanolamine             solution with conc. hydrochloric acid solution.                          

    __________________________________________________________________________     Experiments with ammonium lactate (gel time controlling agent)                 __________________________________________________________________________     solution.                                                                      (a) Gellation of zirconium acetate solution in ammonium lactate solutions                                          Vol.                                             % by       Volume                                                                              Volume                                                                              Volume                                                                              Vol.                                                                               acc-                                       % by  volume     50%  50%  50%  accel-                                                                             eler                                       volume                                                                               ammonium                                                                             Volume                                                                              TEA  DEA  MEA  erator                                                                             ator                                       Zr. acetate                                                                          lactate                                                                              binder                                                                              solution                                                                            solution                                                                            solution                                                                            (a) (b)                                        solution                                                                             solution                                                                             (ml) (ml) (ml) (ml) (ml)                                                                               (ml)                                                                              T gel                                   __________________________________________________________________________     80    20    10   6    --   --   --  -- ≃1 hr                     "     "     10   7    --   --   --  --                                         "     "     10   --   6    --   --  -- 6 min                                   "     "     10   --   7    --   --  -- >6 mins                                 "     "     10   --   4    --   --  -- 5 mins                                  "     "     10   --   5    --   --  -- 21/4 mins                               "     "     10   --   --   2    --  -- no gel                                  "     "     10   --   --   3    --  -- 15 sec                                  "     "     10   --   --   4    --  -- 15 sec                                  "     "     10   --   --   --   3   -- >20 min                                 "     "     10   --   --   --   3.5 -- 41/2 min                                "     "     10   --   --   --   4   -- 1 min                                   90    10    10   4    --   --   --  -- no gel                                  "     "     10   5    --   --   --  -- 11/2 min                                "     "     10   6    --   --   --  -- 30 sec                                  95    5     10   4    --   --   --  -- local-                                                                         ised                                                                           gel                                     "     "     10   --   --   --   --  4  11/4 min                                "     "     10   --   --   --   --  5  10 sec                                  __________________________________________________________________________     MEA - Monoethanolamine                                                                       The ammonium lactate used                                        DEA - Diethanolamine                                                                         throughout is a 60% w/w                                          TEA - Triethanolamine                                                                        solution.                                                        Results obtained using 20 g Mg Cl.sub.2 . H.sub.2 O (gel time                  controlling agent) / 100 ml zirconium acetate-                                 ammonium lactate solution (90:10)                                                      Volume     Volume                                                      Volume  50%        50%  Volume                                                 lactate TEA        MEA  accelerator                                            solution                                                                               solution   solution                                                                            (a)                                                    (ml)    (ml)       (ml) (ml)           T gel                                   __________________________________________________________________________     10      --         6    --             20 secs                                 10      --         --   3              20 secs                                 10      --         --   5              20 secs                                 10      --         --   6              25 secs                                 10      6          --   --             50 secs                                 __________________________________________________________________________     Experiments with ammonium lactate solution                                     (b) Gellation of zetabond 10 - ammonium lactate solutions.                                         Volume                                                                               Volume                                                                               Volume                                                % by volume  50%   50%   accel-                                                ammonium                                                                              Volume                                                                               TEA   MEA   erator                                         % by volume                                                                           lactate                                                                               binder                                                                               soln. soln. (a)                                            zetabond 10                                                                           solution                                                                              (ml)  (ml)  (ml)  (ml)  T gel                                    __________________________________________________________________________     90     10     10    5     --    --    7 min                                    90     "      10    6     --    --    4 min                                    90     "      10    --    --    3     1 min                                                                          20 sec                                   "      "      10    --    --    4     30 sec                                   80     20     10    --    4     --    >20 min                                  "      "      10    --    5     --    >20 min                                  "      "      10    --    --    4     >20 min                                  "      "      10    --    --    5     >20 min                                  85     15     10    --    5     --    3 min                                    "      "      10    --    --    5     5 min                                    "      "      10    --    --    6     8 min                                    __________________________________________________________________________

Accelerator (a) - solution comprising equal volumes of 640P, MEA and water.

Accelerator (b) - solution comprising 2 volumes TEA, 1 volume 640P, 1 volume water.

    __________________________________________________________________________     Experiments with betaine (gel time controlling agent-                          compound which in solution provides a dipolar (Zwitter) ion.                   Results obtained using 10g betaine/100ml zirconium acetate solution                        Volume 50%                                                         Volume betaine                                                                             TEA solution                                                       solution (ml)                                                                              (ml)        T gel                                                  __________________________________________________________________________     10          4           13/4 min                                               10          5           20 sec                                                 __________________________________________________________________________     Results obtained using 10g betaine/100ml zetabond 10 - Solution A                                 Volume                                                             % by volume                                                                           Volume                                                                              50% TEA                                                     % by volume                                                                           solution                                                                              binder                                                                              solution                                                    solution A                                                                            640P I.M.S.                                                                           (ml) (ml) T gel                                                  __________________________________________________________________________     100    --     10   4    11/2 min                                               100    --     10   5    30 sec                                                  50    50     10   2    25 min gels a                                          "      "      10   3    21/2 min                                                                              little                                          "      "      10   4    21/2 min                                                                              soft                                            Results obtained using 20g betaine/100ml Zetabond 10 - solution B:                                Volume                                                                    Volume                                                                              50% TEA                                                     % by volume                                                                           % by volume                                                                           binder                                                                              solution                                                    solution B                                                                            64OP I.M.S.                                                                           (ml) (ml) T gel                                                  __________________________________________________________________________     100    --     10   3    >30 mins                                               "      --     10   4    21/2 mins                                              "      --     10   5    11/4 mins                                              50     50     10   3    9 mins slow                                                                           develop-                                        "      "      10   4    20 mins                                                                               ment of                                                                        gel                                             "      "      10   5    35 mins                                                                               strength                                        70     30     10   3    16 mins                                                                               develop-                                                                       ment of                                         "      "      10   4    9 mins strength                                                                       very                                            "      "      10   5    4 mins slow                                            85     15     10   3    5 mins gels                                                                           develop-                                        "      "      10   4    21/2 mins                                                                             ed                                                                             strength                                        "      "      10   5    3 mins very                                                                           slowly                                          __________________________________________________________________________

    ______________________________________                                         Experiments with fructose (gel time controlling agent)                         ______________________________________                                         (a) Gellation of fructose - zirconium acetate solutions                        Results obtained using 15 g fructose/100 ml zirconium acetate solution:        Vol.                    Vol.                                                   fruc- Vol.     Vol.     50%    Vol.                                            tose  50%      50%      mor-   50%                                             solu- TEA      MEA      pholine                                                                               DEA                                             tion  solution solution solution                                                                              solution                                        (ml)  (ml)     (ml)     (ml)   (ml)   T gel                                    ______________________________________                                         10    --       3        --     --     2 mins                                   10    --       4        --     --     51/2 mins                                10    --       6        --     --     11/2 mins                                10    --       --       4      --     81/2 mins                                10    --       --       5      --     5 mins                                   10    --       --       6      --     31/2 mins                                Results obtained using 10 g fructose/100 ml zirconium acetate solution:        Vol.                    Vol.                                                   fruc- Vol.     Vol.     50%    Vol.                                            tose  50%      50%      mor-   50%                                             solu- TEA      MEA      pholine                                                                               DEA                                             tion  solution solution solution                                                                              solution                                        (ml)  (ml)     (ml)     (ml)   (ml)   T gel                                    ______________________________________                                         10    --       5        --     --     immediate                                                                      gellation                                10    --       --       5      --     immediate                                                                      gellation                                10    5        --       --     --     31/4 mins                                 10   --       --       --     4      1 min                                                                          20 sec                                   10    --       --       --     5      11/2 mins                                (b) Gellation of fructose - zetabond 10 solution                               Results obtained using 10g fructose/100 ml zetabond 10                         Volume    Volume     Volume 50%                                                fructose  50% MEA    morpholine                                                solution  solution   solution                                                  (ml)      (ml)       (ml)       T gel                                          ______________________________________                                         10        5          --         2 mins                                         10        --         5          61/2 mins                                      10        --         6          3 mins                                         ______________________________________                                         (c) Gellation of fructose - zetabond 5 solution                                Results obtained using 10g fructose/100 ml zetabond 5:                                              Volume 50%                                                Volume fructose                                                                          Volume 50% morpholine                                                solution (ml)                                                                            TEA solution                                                                              solution    T gel                                         ______________________________________                                         10        5          --          25 secs                                       10        --         5           localised                                                                      gellation                                     ______________________________________                                          (d) Gellation of fructose - magnesium chloride -                              zirconium acetate solutions                                                    Results obtained using 15 g fructose and 20 g magnesium                        chloride (hydrated)/100 ml zirconium acetate solution:                         Volume  Volume    Volume                                                       fructose                                                                               50% TEA   50% morpholine                                               solution                                                                               solution  solution                                                     (ml)    (ml)      (ml)               T gel                                     ______________________________________                                         10      --        5                                                            10      --        6                  gellation                                                                      did not                                   10      5         --                 occur                                     10      6         --                                                           ______________________________________                                         Results obtained using 15 g fructose and 10 g magnesium                        chloride (hydrated)/100 ml zirconium solution:                                 Volume  Volume    Volume                                                       fructose                                                                               50% MEA   50% morpholine                                               solution                                                                               solution  solution                                                     (ml)    (ml)      (ml)               T gel                                     ______________________________________                                         10      6         --                 gellation                                                                      did not                                   10      --        6                  occur                                     ______________________________________                                         Results obtained using 15 g fructose and 5 g magnesium                         chloride (hydrated)/100 ml zirconium acetate solution:                         Volume  Volume    Volume                                                       fructose                                                                               50% MEA   50% morpholine                                               solution                                                                               solution  solution                                                     (ml)    (ml)      (ml)             T gel                                       ______________________________________                                         10      6         --               5 mins                                      10      --        6                61/2 mins                                   ______________________________________                                         Results obtained using 12 g fructose and 8 g magnesium                         chloride (hydrated)/100 ml zirconium acetate solution:                                Volume    Volume     Volume                                             Volume 50%       50%        50%                                                fructose                                                                              MEA       morpholine DEA                                                solution                                                                              solution  solution   solution                                           (ml)   (ml)      (ml)       (ml)    T gel                                      ______________________________________                                         10     5         --         --      11/2 mins                                  10     6         --         --      2 mins                                                                         15 secs                                    10     --        4          --      6 mins                                     10     --        5          --      3 mins                                                                         20 secs                                    10     --        6          --      2 mins                                                                         15 secs                                    10     --        --         6       25 mins                                    ______________________________________                                         Results obtained using 10 g fructose and 10 g magnesium                        chloride (hydrated)/100 ml zirconium acetate solution:                                Volume    Volume     Volume                                             Volume 50%       50%        50%                                                fructose                                                                              MEA       morpholine DEA                                                solution                                                                              solution  solution   solution                                           (ml)   (ml)      (ml)       (ml)    T gel                                      ______________________________________                                         10     4         --         --      25 secs                                    10     5         --         --      30 secs                                    10     6         --         --      30 secs                                    10     --        5          --      localised                                                                      gellation                                  10     --        --         5       21/2 mins                                  10     --        --         6       33/4 mins                                  ______________________________________                                         Results obtained using 10g fructose and 5g magnesium -chloride                 (hydrated)/100 ml zirconium acetate solution:                                  Volume   Volume      Volume                                                    fructose 50% MEA     gelling                                                   solution solution    agent (a)                                                 (ml)     (ml)        (ml)        T gel                                         ______________________________________                                         10       3           --          45 secs                                       10       6           --          1 min. 15 secs                                10       --          6           3 mins 15 secs                                ______________________________________                                         Gelling agent (a) - solution comprising equal volumes of                       MEA, 64OP and water                                                            Results obtained using 10g fructose and 4g magnesium                           chloride (hydrated)/100 ml zirconium acetate solution:                         Volume      Volume                                                             fructose    gelling                                                            solution    agent (a)                                                          (ml)        (ml)          T gel                                                ______________________________________                                         10          5             1 min. 20 secs                                       10          6             1 min.                                               ______________________________________                                    

    __________________________________________________________________________     Experiments with sorbitol.                                                     (a) Gellation of sorbitol (gell time controlling agent) -                      zirconium acetate solutions.                                                   Results are given overleaf                                                     Weight sorbitol (gms)                                                                       Volume Volume                                                     dissolved in 100 ml                                                                         sorbitol                                                                              50% TEA                                                    zirconium acetate                                                                           solution                                                                              solution                                                   solution     (ml)   (ml)   T gel                                               __________________________________________________________________________     5            10     5        1 min                                             "            10     6        25 secs                                           7            10     4        >30 mins                                          "            10     5        1 min                                                                          45 secs                                           "            10     6        1 min                                                                          45 secs                                           "            10     5        34 mins                                           10           10     6        13 mins                                           "            10     7        12 mins                                           20           10     5        gellation                                                                      did not                                           "            10     6        occur                                             "            10     7                                                          __________________________________________________________________________     (b) Gellation of sorbitol-zetabond 10 solutions                                Results obtained using 7g sorbitol/100 ml zetabond 10:                         Composition of gelling agent                                                                           Volume                                                                              Volume                                                          % by % by sorbitol                                                                            gelling                                           % by volume                                                                           % by volume                                                                           volume                                                                              volume                                                                              solution                                                                            agent                                             TEA    MEA    water                                                                               64OP (ml) (ml)   T gel                                      __________________________________________________________________________     50     --     50   --   10   5      >1 hr                                      "      --     "    --   10   6                                                 --     50     --   50   10   5      >1 hr                                      --     "      --   "    10   6                                                 __________________________________________________________________________     Results obtained using 5g sorbitol/100 ml zetabond 10:                         Composition of gelling agent                                                                        Volume                                                                               Volume                                              % by % by  % by % by sorbitol                                                                             gelling                                             volume                                                                              volume                                                                               volume                                                                              volume                                                                              solution                                                                             agent                                               TEA  MEA   water                                                                               64OP (ml)  (ml)  T gel                                         __________________________________________________________________________     50   --    50   --   10    5     No gel                                        "    --    "    --   10    6     15 mins                                       --   50    --   50   10    6     21/2 mins                                     --   "     --   "    10    7     50 secs                                       --   35    15   50   10    3     No gel                                        --   "     "    "    10    4     75 secs                                       --   "     "    "    10    5     30 secs                                       __________________________________________________________________________     Results obtained using 2g sorbitol/100ml zetabond 10:                          Composition of binder                                                                     Composition of gelling agent                                                                   Volume                                                                         sorbit-                                                                             Vol.                                           % by volume                                                                           % by                                                                               % by                                                                               % by                                                                               % by                                                                               % by                                                                               ol sol-                                                                             gel.                                           sorbitol                                                                              vol.                                                                               vol.                                                                               vol.                                                                               vol.                                                                               vol.                                                                               ution                                                                               agent                                          solution                                                                              64OP                                                                               TEA MEA water                                                                              64OP                                                                               (ml) (ml)                                                                              T gel                                       __________________________________________________________________________     100    --  50  --  50  --  10   4  7 mins                                      "--    "   --  "   --  10  5    45 secs                                        80     20  50  --  50  --  10   4  2 mins                                      "      "   "   --  "   --  10   5  1 min                                       "      "   --  35  15  50  10   3  10 secs                                     "      "   --  "   "   "   10   4  spontan-                                                                       eous                                                                           gellat-                                                                        ion.                                        __________________________________________________________________________     (c) Gellation of sorbitol-magnesium chloride-zirconium                         acetate solutions                                                              Results obtained using 10g sorbitol and 6g magnesium                           chloride (hydrated)/100 ml zirconium acetate solution:                                    Volume     Volume                                                   Volume sorbitol                                                                           50% TEA    gelling                                                  solution   solution   agent (a)                                                (ml)       (ml)       (ml)       T gel                                         __________________________________________________________________________     10         5          --         40 secs                                       10         6          --         50 secs                                       10         --         5          31/2 mins                                     10         --         6          2 mins                                        __________________________________________________________________________     Results obtained using 5g sorbitol and 10g magnesium                           chloride (hydrated)/100ml zirconium acetate solution:                                     Volume     Volume                                                   Volume sorbitol                                                                           50% TEA    gelling                                                  solution   solution   agent (a)                                                (ml)       (ml)       (ml)       T gel                                         __________________________________________________________________________     10         6          --         20 secs                                       10         --         6          localised                                                                      gellation                                     __________________________________________________________________________

    __________________________________________________________________________     Experiments with glycine (compound which in solution provides                  dipolar (Zwitter) ions - gellation time controlling agent).                    (a) Gellation of glycine-zirconium acetate solutions.                          Results are given overleaf:                                                    Composition of binder                                                          Weight glycine       Volume                                                                              Volume                                               (gms)/100ml                                                                            % by         50%  50%  Volume                                          zirconium                                                                              volume                                                                              % by                                                                               Volume                                                                             TEA  MEA  gelling                                         acetate glycine                                                                             volume                                                                             binder                                                                             solution                                                                            solution                                                                            agent (a)                                       solution                                                                               solution                                                                            640P                                                                               (ml)                                                                               (ml) (ml) (ml)  T gel                                     __________________________________________________________________________     15      100  --  10  --   3    --    40 secs                                   "       "    --  10  --   4    --    15 secs                                   "       "    --  10  --   6    --    15 secs                                   "       "    --  10  --   --   4     1 min                                     "       "    --  10  --   --   6     25 secs                                   10      "    --  10  4    --   --    no gel                                    "       "    --  10  5    --   --    28 mins                                   "       "    --  10  6    --   --    3 mins                                     5      "    --  10  5    --   --    21/2 mins                                 "       "    --  10  6    --   --    50 secs                                    1      "    --  10  5    --   --    20 secs                                   10      80   20  10  5    --   --    15 mins                                   "       "    "   10  6    --   --    20 mins                                    5      "    "   10  5    --   --    21/2 mins                                 "       "    "   10  6    --   --    70 secs                                    1      60   40  10  5    --   --    20 secs                                   __________________________________________________________________________     (b) Gellation of glycine-zetabond 5 solution.                                  Results obtained using 21/2g glycine/100 ml zetabond 5:                        Volume     Volume                                                              glycine    50% TEA                                                             solution   solution                                                            (ml)       (ml)      T gel                                                     __________________________________________________________________________     10         4         8 mins                                                    10         5         50 secs                                                   __________________________________________________________________________     Experiments with glycerol.                                                     (a) Gellation of glycerol (gellation time controlling                          agent) - zirconium acetate solution.                                           Results obtained are given below:                                              Composition of binder                                                           % by                                                                          volume            Volume                                                       zirconium                                                                            % by  Volume                                                                               gelling                                                      acetate                                                                              volume                                                                               binder                                                                               agent(b)                                                     solution                                                                             glycerol                                                                             (ml)  (ml)   T gel                                                 __________________________________________________________________________     80    20    10    4      30 secs                                               "     "     10    6      35 secs                                               __________________________________________________________________________     (b) Gellation of glycerol-zetabond 10 solutions.                               Following results were obtained:                                               Composition of binder  Volume                                                  % by             Volume                                                                               50%                                                     volume                                                                               % by  Volume                                                                              gelling                                                                              TEA                                                     zetabond                                                                             volume                                                                               binder                                                                              agent (b)                                                                            solution                                                10    glycerol                                                                             (ml) (ml)  (ml) T gel                                              __________________________________________________________________________     90    10    10   6     --   2 mins                                             80    20    10   5     --   4 mins                                             "     "     10   6     --   5 mins                                             "     "     10   --    5    2 mins                                             "     "     10   --    6    3 mins                                             __________________________________________________________________________     (c) Gellation of glycerol-magnesium chloride-zirconium                         acetate solutions.                                                             Results obtained using 17g magnesium chloride (hydrated)/                      100 ml zirconium acetate solution - glycerol solution (80:20)                                  Volume                                                         Volume  Volume  50%                                                            Glycerol                                                                               gelling TEA                                                            solution                                                                               agent (b)                                                                              solution                                                       (ml)    (ml)    (ml)    T gel                                                  __________________________________________________________________________     10      6       --      4 mins                                                 10      --      5       11/4 mins                                              10      --      6       11/2 mins                                              __________________________________________________________________________     Gelling agent (b) - solution comprising 2 parts by volume TEA,                 1 part of 640P and 1 part of water.                                            __________________________________________________________________________

    __________________________________________________________________________     Experiments with amino-alcohols other than the ethanolamines                   as gellation inducing agents.                                                  (a) Gellation of zetabond 10.                                                  Results obtained are given below:                                                                    Volume       Volume                                                            50%          50%                                         Composition of binder                                                                           Volume                                                                              solution                                                                               Volume                                                                              solution                                    % by             50%  2-amino 50%  2-amino                                     volume                                                                               % by  Volume                                                                              solution                                                                            2-methyl 1:3                                                                           solution                                                                            2 ethyl-1:3                                 zetabond                                                                             volume                                                                               binder                                                                              TM   propanediol                                                                            AMP  propanediol                                 10    640P  (ml) (ml) (ml)    (ml) (ml)    T gel                               __________________________________________________________________________     100   --    10   4    --      --   --      No gel                              "     --    10   5    --      --   --      7 mins                              90    10    10   5    --      --   --      4 mins                              80    20    10   3    --      --   --      no gel                              "     "     10   4    --      --   --      7 mins                              "     "     10   5    --      --   --      5 mins                              70    30    10   5    --      --   --      8 mins                              "     "     10   6    --      --   --      13 mins                             100   --    10   --   5       --   --      no gel                              "     "     10   --   6       --   --      20 secs                             80    20    10   --   5       --   --      40 secs                             100   --    10   --   --      5    --      localised                                                                      gellation                           "     --    10   --   --      --   6       45 secs                             __________________________________________________________________________     (b) Gellation of zetabond 30                                                   Following results obtained:                                                    Composition of binder                                                                            Volume                                                       % by              50%                                                          volume                                                                               % by  Volume                                                                               solution                                                     zetabond                                                                             volume                                                                               binder                                                                               TM                                                           30    640P  (ml)  (ml)  T gel                                                  __________________________________________________________________________     100   --    10    6     8 mins                                                 80    20    10    5     18 mins                                                "     "     10    6     30 mins                                                __________________________________________________________________________     Note:                                                                              AMP - 2-amino-2-methyl 1-propanol                                              TM - Tri (hydroxymethyl) methylamine                                       (c) Gellation of magnesium lactate-zirconium acetate                           solution.                                                                      Results obtained using 10g magnesium lactate/100 ml zirconium                  acetate solution.                                                              Volume  Volume  Volume                                                         lactate 50% TM  50% AMP                                                        solution                                                                               solution                                                                               solution                                                       (ml)    (ml)    (ml)    T gel                                                  __________________________________________________________________________     10      6       --      15 mins                                                10      7       --      12 mins -10 8 -- 10 mins                               10      --      5       localised                                                                      gellation                                              __________________________________________________________________________     Results obtained using 5g magnesium lactate/100ml acetate                      solution:                                                                      Volume    Volume                                                               lactate   50% TM                                                               solution  solution                                                             (ml)      (ml)       T gel                                                     __________________________________________________________________________     10        5          No gel                                                    10        6          2 mins 45 secs                                            10        7          1 min 45 secs                                             __________________________________________________________________________     Results obtained using 21/2g magnesium lactate/100ml zirconium                 acetate solution:                                                              Volume    Volume                                                               lactate   50% TM                                                               solution  solution                                                             (ml)      (ml)       T gel                                                     __________________________________________________________________________     10        5          2 mins.                                                   __________________________________________________________________________

    ______________________________________                                         Experiments with mannitol                                                      (a) Gellation of mannitol-magnesium chloride-zirconium                         acetate solution.                                                              Results obtained using 10g mannitol and 10g magnesium                          chloride (hydrated)/100ml zirconium acetate solution:                          Volume mannitol                                                                            Volume gelling                                                     solution (ml)                                                                              agent (b)      T gel                                               ______________________________________                                         10          3              No gel                                              10          4              2 mins                                              10          6              20 secs                                             ______________________________________                                         Gelling agent (b) - solution comprising 2 parts by                             volume TEA, 1 part of water and 1 part of 640P.                           

    __________________________________________________________________________     Weight of                                                                      magnesium                                                                             Composition of gelling agent                                                                   Volume                                                                              Volume                                             lactate                                                                               % by                                                                               % by                                                                               % by                                                                               % by                                                                               lactate                                                                             gelling                                            (gm)/100ml                                                                            volume                                                                             volume                                                                             volume                                                                             volume                                                                             solution                                                                            agent                                              Zr acetate                                                                            TEA DEA water                                                                              640P                                                                               (ml) (ml) T gel                                         __________________________________________________________________________     4      50  --  50  --  10   4    1 hr.                                         "      "   --  "   --  10   5    30 secs.                                      10     "   --  "   --  10   5    8 mins.                                                                               firm gels                              "      "   --  "   --  10   6    4 mins.                                                                               on standing                            "      "   --  "   --  10   7    3 mins.                                       "      --  50  50  --  10   3    >70 mins.                                     "      --  "   "   --  10   4    75 secs                                       "      --  50  --  50  10   4    21/2 mins.                                                                            firm                                   "      --  "   --  "   10   5    3 mins.                                                                               gels on                                "      --  "   --  "   10   6    10 mins.                                                                              standing                               __________________________________________________________________________

Example XXII Experiments with Steetley's Ceramic Powder - MCH Grade and the Refractory Binder Based on Zirconium Acetate Solution

Steetley ceramic powder is a spinel based refractory powder having the approximate composition given in Example VII. It thus contains its own gel inducing agent.

Bonding of a refractory aggregate consisting of 2 parts by weight of Steetley ceramic powder MCH 45 and 1 part by weight of Steetley ceramic powder MCH 200 was attempted using zirconium acetate solution (22% ZrO₂) in which a suitable additive had been dissolved. Data showing the effect of various additives on gellation behaviour are given below. For the preparation of shaped refractory objects, the refractory aggregate and binder medium were used in the proportion of 100 g refractory aggregate to 20 ml binder medium.

    __________________________________________________________________________     (a) Effect of magnesium acetate crystals (CH.sub.3 COO).sub.2 Mg 4H.sub.2      O (See Example VII)                                                            Weight of magnesium                                                            acetate crystals (gms)                                                         dissolved in 100 ml of                                                                            Setting time                                                zirconium acetate  of slurry                                                   solution           (min)       Comments                                        __________________________________________________________________________              0           21/2                                                              10           33/4      rapid                                                   20           43/4      development                                             30           61/4      of strength                                             40           11                                                        __________________________________________________________________________     (b) Effect of magnesium acetate (dried) (CH.sub.3 COO).sub.2 Mg H.sub.2        Weight of magnesium                                                            acetate (gms) dis-                                                             solved in 100 ml   Setting time                                                zirconium acetate  of slurry                                                   solution           (min)       Comments                                        __________________________________________________________________________              0           21/2      good devel-                                             10           41/4                                                                                     opment of                                               20           7         strength                                                30           45        did not                                                                        harden completely                               __________________________________________________________________________             (c) Effect of magnesium Lactate                                        Weight of                                                                      magnesium                                                                      lactate (gms)                                                                  dissolved in                                                                           Volume         Volume                                                  100 ml zircon-                                                                         lactate   Volume                                                                              ethylene                                                                            Volume                                             ium acetate                                                                            solution  glycerol                                                                            glycol                                                                              740P                                                                               Setting                                        solution                                                                               (ml)      (ml) (ml) (ml)                                                                               Time                                           __________________________________________________________________________     0       20        --   --   --  21/2 min.rapid dev-                            4       20        --   --   --  4min. elopment of                              10      20        --   --   --  5min.strength                                  4       17.5      2.5  --   --  10min.                                         "       15        5    --   --  slurry thickened but                                                           did not harden                                 "       15        --   5    --  4min.rapid dev-                                                                 elopment of                                   "       15        --   --   5   4min.strength                                  __________________________________________________________________________             (d) Effect of sorbitol                                                         Weight sorbitol                                                                (gm) dissolved                                                                 in 100 ml zircon-                                                                             Setting time                                                    ium acetate    of slurry                                                       solution       (mins.)  Comments                                       __________________________________________________________________________                0           21/2                                                              10           12       fairly rapid increase                                                          in viscosity initially                                   11           17       development of stre-                                                           ngth somewhat slow                                       12           30                                                                                      slurry immobile                                          15                    after 25 mins, still                                                           soft after 40 mins,                                      20                    slurry thickened but                                                           still rather soft                                                              after several hours                            __________________________________________________________________________             (e) Effect of mannitol                                                         Weight of mannitol                                                             (gm) dissolved in                                                              100 ml zirconium                                                                              Setting time                                                    acetate solution                                                                              of slurry                                               __________________________________________________________________________                 0          21/2 mins.                                                          5          41/2 mins.                                              __________________________________________________________________________             (f) Effect of fructose                                                         Weight of fractone                                                             (gm) dissolved in                                                              100 ml zirconium                                                                              Setting time                                                    acetate solution                                                                              of slurry                                                                               Comments                                       __________________________________________________________________________                 0          21/2 mins.                                                          5           4 mins. developed strength                                        10          13 mins. on standing                                               15          Immobile after 35 mins.,                                           20          did not harden slurry                                                          became viscous but did                                                         not harden                                              __________________________________________________________________________             Note: magnesium citrate and magnesium oxalate are                              insoluble in zirconium acetate solution.                                       (g) Effect of diluents                                                         In this case 15 ml binder medium used with 100 g refractory                    aggregate                                                              __________________________________________________________________________     Volume                                                                         zirconium   Volume                                                                               Volume                                                       acetate                                                                               Volume                                                                              740P  ethylene                                                                             Volume                                                                               Setting                                          solution                                                                              water                                                                               I.M.S.                                                                               glycol                                                                               glycerol                                                                             time                                             (ml)   (ml) (ml)  (ml)  (ml)  (mins.)                                          __________________________________________________________________________     10      5   --    --    --    11/2                                             7.5    7.5  --    --    --    11/4    very good                                 5     10   --    --    --    50 secs.                                                                               green                                    10     --    5    --    --    21/4    strength                                 7.5    --   7.5   --    --    21/4                                              5     --   10    --    --    21/2                                             10     --   --    5     --    21/4                                             7.5    --   --    7.5         slurry did not harden                            12.5   --   --    --    2.5   21/4                                             10     --   --    --    5.0   slurry did not harden                            __________________________________________________________________________

Example XXIII Use of Alkali Metal Borates to Control Setting Time of Slurry of Zetabond 10 and Steetley Ceramic Powder

The tetraborates of lithium, potassium and sodium display strong retarding effects on the rate of setting of slurries of zetabond 10 and refractory powders of the MCH type. Of the tetraborates used, the sodium salt (borax) proved to be most satisfactory on account of its ready solubility in zetabond 10.

Experiments with Sodium Tetraborate (Borax)

The appropriate quantity of borax was dissolved in a solution comprising equal volumes of zetabond 10 and 640P. A slurry was obtained by mixing 30 ml. binding medium with 200 g refractory aggregate. (The latter consisted of 2 parts by weight MCH-7+22, 1 part by weight MCH 85 and 2 parts by weight MCH 200) The slurry was poured into a cylinder mould and the setting time noted (see below). After hardening, the shaped article was removed from the mould, ignited to burn off the alcohol and then fired at 100° C. for four hours.

    ______________________________________                                         Weight borax (gms)                                                             dissolved in 100ml                                                             of zetabond (10/640P                                                                              Setting time                                                solution (1:1)     of slurry                                                   ______________________________________                                         0                  70 secs.                                                    1/2                23/4 mins.                                                  11/4               31/2 mins.                                                  21/2               5 mins.                                                     5.0                8 mins.                                                     15                 15 mins.                                                    ______________________________________                                    

With zirconium acetate solution containing no magnesium acetate, much lower setting times are obtained as indicated in the following table.

    ______________________________________                                         Weight borax (gms)                                                             dissolved in 100ml                                                             of acetate solution/                                                                              Setting time                                                640P (1:1)         of slurry                                                   ______________________________________                                         0                  40 secs.                                                    21/2               21/2mins.                                                   5                  31/4 mins.                                                  71/2               51/2 mins.                                                  ______________________________________                                    

Experiments with Lithium Tetraborate

Using lithium tetraborate in place of borax and following the procedure adapted previously, the following data were obtained.

    ______________________________________                                         Weight of lithium                                                              tetraborate (gms)                                                              dissolved in 100ml                                                             of zetabond 10/640P                                                                               Setting time                                                solution (1:1)     of slurry                                                   ______________________________________                                         0                  70 secs.                                                    1/2                31/4 mins.                                                  11/4               41/4 mins.                                                  21/2               8 mins.                                                     ______________________________________                                    

Experiments with Potassium Tetraborate

Potassium tetraborate has only limited solubility in zetabond 10 ≃ 1g 1100 ml solution) and is, therefore, unsatisfactory. Using 1 g potassium tetraborate/100 ml zetabond 10/640P solution (1:1) - setting time of slurry 23/4 mins. As alternatives to magnesium acetate, magnesium chloride (anhydrous), ammonium magnesium chloride and calcium formate were selected but were shown, under a wide range of conditions, to be ineffective in preventing localised gelation.

Example XXIV Experiments with B40 Basic Refractory Aggregate and the Refractory Binder Based on Zirconium Acetate Solution

Slurries were prepared by mixing 25 ml binder medium (zirconium acetate containing gellation controller) with 200 g refractory aggregate and the setting time of the slurry was noted.

    __________________________________________________________________________     (1) Effect of magnesium acetate crystals (CH.sub.3 COO).sub.2 Mg4H.sub.2       __________________________________________________________________________     weight of magne-                                                               sium acetate (gms)                                                                        Volume    Volume                                                    dissolved in zir-                                                                         acetate                                                                             Volume                                                                              ethylene                                                  conium acetate                                                                            solution                                                                            glycerol                                                                            glycol                                                                               Setting                                             solution   (ml) (ml) (ml)  time                                                __________________________________________________________________________      0         25   --   --   70 secs. quite hard                                  20         25   --   --   21/2 mins.                                           30         25   --   --   3 mins.                                              40         25   --   --   6 mins. somewhat soft                                10         20   5    --   slurry did not harden                                10         22.5 2.5  --   slurry did not harden                                10         20   --   5    2 mins.                                              10         25   --   10   slurry thickened after                                                         3 mins. but did not                                                            harden completely                                    (2) Effect of magnesium acetate (dried) (CH.sub.3 COO).sub.2 MgH.sub.2         __________________________________________________________________________     Weight of magnesium                                                            acetate (gms) dis-                                                             solved in zirconium                                                            acetate solution         Setting time                                          __________________________________________________________________________      0                       70 secs.                                               5                       11/2 mins.                                            10                       2 mins.                                               20                       31/2 mins.                                            __________________________________________________________________________

Example XXV Preparation of Monolithic Ceramic Shell Moulds

A coating composition was prepared by dispersing 1000 g of Molochite - 120 grade in 400 ml of a solution of magnesium acetate in zirconium acetate solution. A ceramic shell mould was prepared as follows:

STAGE 1

A wax pattern was dipped into the coating composition, then dusted with a powder comprising a mixture of Steetley Ceramic Powder MCH 200 - 1 part by weight and Steetley Ceramic Powder MCH-8+22 - 3 parts by weight. The coating on the pattern was allowed to harden by standing for ten minutes in air.

STAGES 2, 3, and 4

As Stage 1. The shell was left overnight for hardening to be completed. A firm hard shell was obtained, with good resistance to removal of particles by mechanical abrasion. The shell may be dewaxed and fired following standard known procedures.

An alternative powder for dusting is a mixture of Steetley Ceramic Powder MCH200 - 1 part by weight, Steetley Ceramic Powder MCH45 - 3 parts by weight.

It is frequently advantageous to apply a sealing coat to the shell by dipping it into the coating composition before it is left overnight for hardening to be completed. If desired, a known primary coating may be applied to the wax pattern prior to the first stage of the ceramic shell mould formation.

Example XXVI Effect of Alcohol as Diluent of Solution of Magnesium Acetate in Zirconium Acetate Solution Used to Bind Steetley Ceramic Powder

The solution of magnesium acetate in zirconium acetate solution was prepared by dissolving 10.0 g of magnesium acetate crystals (4H₂ O) in 100 ml of the zirconium acetate solution. The aggregate used was

Steetley Ceramic Powder MCH 45-- 4 parts by weight

Steetley Ceramic Powder MCH 200-- 4 parts by weight

Steetley Ceramic Powder MCH-8+25- 1 part by weight

200 g of the above aggregate were used with 35 ml of the binder solution to form a slurry. The slurry was poured into a cylinder mould, 2 inches diameter, then allowed to set. After setting, the cylinder was removed from the mould, ignited to burn off the alcohol and remove water, then fired at 1450° C. for four hours. The cold crushing strength of the cylinder was determined after firing. Results obtained are given in the table.

    ______________________________________                                         Binder Composition                                                             ______________________________________                                         % by volume                                                                    zirconium               Crushing strength                                      acetate - mag-          (lbs/in.sup.2) after firing                            nesium acetate                                                                            % by volume  at 1450° C for four                             solution   640P I.M.S.  hours                                                  ______________________________________                                         100        NIL          710                                                    75         25           540                                                    50         50           300                                                    ______________________________________                                    

The binder compositions 75:25 and 50:50 zirconiumacetate - magnesium acetate solution and 640P I.M.S. respectively may be used in conjunction with the aggregate to prepare moulds, part-moulds of cores for the casting of metals by a process in which the powdered refractory aggregate is mixed with the binder composition to form a pourable slurry and including the steps of igniting the solvent alcohol escaping from the surface of the mould as soon as the slurry is set by gelling, the mould being supported during the burning of the alcohol in such a way that there is free circulation around all surfaces of the mould so that ignition and burning of the alcohol occurs evenly from all surfaces. This type of process is described in British Patent Specification No. 716,394.

Example XXVII Use of Dead Burned Magnesia as Gelling Agent with Solution of Magnesium Acetate in Zirconium Acetate Solution

The dead burned magnesia used in this and the ensuing Examples is prepared by ball-milling a dead-burned Sardinium magnesia pellet. The analysis of the material used was

    ______________________________________                                         Fe.sub.2 O.sub.3 0.22%                                                         Al.sub.2 O.sub.3 0.25%                                                         CaO              1.62%                                                         SiO.sub.2        .78%                                                          BET surface area 2m.sup.2 /g (approx.)                                         ______________________________________                                    

Surface area by Rigden method 0.25- 0.30 m² /g Solutions of magnesium acetate in zirconium acetate solution were prepared by dissolving the appropriate amount of magnesium acetate crystals (4H₂ O) in zirconium acetate solution.

Experiments with Fine Sillimanite Mix

10% by weight of dead burned magnesia was added to the fine sillimanite mix. The results obtained are given in the table.

    __________________________________________________________________________            Weight of                                                                      magnesium ace-                                                                 tate crystals                                                           Weight of                                                                             (gms) per 100                                                                           Volume of                                                      refractory                                                                            ml zirconium                                                                            solution                                                                             Gel time                                                 powder (gms)                                                                          acetate solution                                                                        used (ml)                                                                            (mins)                                                                              Observations                                        __________________________________________________________________________     200    10       35    31/2 slow uniform                                                                   set, very hard                                      200    10       35    3    volume of solution                                                             used contained 20                                                              v/v 740P I.M.S.                                                                Easier to pour.                                                                Set very hard                                       200    40       35    5    Thick syrupy                                                                   slurry which                                                                   hardened slowly                                     1500   40       300   4    volume of solution                                                             used contained 20                                                              v/v 740P I.M.S.                                                                slow to harden                                      __________________________________________________________________________

Example XXVIII

    ______________________________________                                         The molochite mix used was                                                     Molochite 1/4 on 8 grade                                                                          1 part by weight                                            Molochite 8-16 grade                                                                              1 part by weight                                            Molochite 16-30 grade                                                                             1 part by weight                                            Molochite -120 grade                                                                              2 parts by weight                                           ______________________________________                                    

5% by weight of DSP2 "fines" magnesia was added to the above mix. The binding liquid used was a mixture of one part by volume of 640P I.M.S. and two parts by volume of a solution of 10.0 g magnesium acetate crystals in 100 ml of zirconium acetate solution. 75 ml of this binding liquid per pound of refractory powder mix gave a slurry which had a setting time of 5 minutes. The "green strength" was very good. A suitable firing schedule is 1480° C. for 11/2 hours.

Example XXIX

    ______________________________________                                         Experiments with silicon carbide mix                                           ______________________________________                                         The silicon carbide mix used was                                               Sika silicon carbide 8-14 grade                                                                     2 parts by weight                                                              Sika silicon carbide 14-36 grade                                                2 parts by weight                                                             Sika silicon carbide 36-100 grade                                               1 part by weight                                                              Carborundum silicon carbide                                                     2 parts by weight                                                              2F grade                                                 ______________________________________                                    

5% by weight of DSP2 "fines" magnesia was added to the above mix. The binding liquid used was a mixture of one part by volume of 640P I.M.S. and three parts by volume of a solution of 10.0 g magnesium acetate crystals in 100 ml of zirconium acetate solution. 65 ml of this binding liquid per pound of refractory powder mix gave a slurry which had a setting time of about five minutes. The "green strength" was very good. A suitable firing schedule is 1550° 1600° C., gradually increasing over a period of three hours.

Example XXX Manufacture of Well Blocks for the Discharge Valves of Casting Ladles

Well blocks are made as follows. The binding liquid used is a mixture of one part by volume of 640P I.M.S. and three parts by volume of a solution of 10.0 g magnesium acetate crystals in 100 ml of zirconium acetate solution. To 100 parts by weight of the mixture of sintered mullite of the same type as used in Example XIII, calcined alumina and tabular alumina grains is added 5 parts by weight of DSP2 `fines` magnesia. 65 ml of the binding liquid per pound of refractory grain gives a slurry which has a setting time of about 5 minutes. The `green strength` was very good. A suitable firing schedule is 1550° 1600° C., gradually increasing over a period of three hours.

Example XXXI Manufacture of Orifice Rings for Pouring Molten Glass in Bottle Manufacture

Orifice rings may be made using dead burned magnesia as gelling agent with a solution of magnesium acetate in zirconium acetate solution. To a suitable refractory mix is added 5% by weight of DSP2 "fines" magnesia. The binding liquid is a mixture of one part by weight of 640P I.M.S. and either two or three parts by volume of a solution of 10.0 g magnesium acetate crystals in 100 ml of zirconium acetate solution.

Example XXXII

    ______________________________________                                         Preparation of piece moulds                                                    ______________________________________                                         Using as refractory grain a powder mix comprising:                             ______________________________________                                         Zircon sand                                                                                    1/3 part by weight                                                             Zircon flour                                                                    1/3 part by weight                                                            Calcined fireclay                                                               1/3 part by weight                                            ______________________________________                                    

Suitable proportions are 140 g dead burned magnesia fines with 1590 g of the above refractory grain, together with 125 ml zetabond C and 125 ml of ethyl alcohol. The setting time of the slurry is about 100 seconds. Leave for 100- 120 seconds before stripping from the pattern. This gives a mould with good surface finish, good reproduction of detail, also adequate strength after burning off the alcohol solvent.

With 50 g dead burned magnesia fines, the setting time of the slurry is about 5 minutes.

A strong mould may be obtained by using 140 g dead burned magnesia fines with 159g of the above refractory grain, together with 10.0 g borax dissolved in 125 ml zetabond C, with 125 ml ethyl alcohol. The setting time of the slurry is about 5 minutes. Mould had good surface finish and good reproduction of detail. After burning off the alcohol solvent a stronger mould was obtained.

Moulds, part-moulds or cores may be made by the above technique, in which the powdered refractory aggregate is mixed with the binder to form a pourable slurry and including the steps of igniting the solvent alcohol escaping from the surface of the mould as soon as the slurry is set by gelling, the mould being supported during the burning of the alcohol in such a way that there is free circulation around all surfaces of the mould so that ignition and burning of the alcohol occurs evenly from all surfaces. This type of process is described in British Patent Specification No. 716,394. The moulds part-moulds or cores are suitable for the coating of metals and/or alloys.

Example XXXIII Manufacture of Piece Moulds having a Mixture of Steetley MCH Powder Grains

    ______________________________________                                         Component No. 1 is a mixture of the following MCH                              powder grains, parts by weight:                                                         MCH -7+22                                                                       2 parts                                                                       MCH 85                                                                          1 part                                                                        MCH 200                                                                         2 parts                                                              Component No. 2 is MCH 3/16 + 7                                                         Suitable proportions are:-                                                     Component No. 1                                                                 380 parts                                                                     Component No. 2                                                                 140 parts                                                            ______________________________________                                    

This powder mix was used with 5.0 5.0g borax dissolved in 125 ml zetabond C and 125 ml ethyl alcohol. The time required to mix the slurry was about 30 seconds, the setting time of the slurry being about 3 minutes. Leave for about 5 minutes before stripping the pattern. The mould had a good surface finish and good reproduction of detail. A strong mould was obtained on burning off the alcohol solvent.

Moulds, part-moulds or cores may be made by the above techniques in which the powdered refractory aggregate is mixed with the binder to form a pourable slurry and including the steps of igniting the solvent alcohol escaping from the surface of the mould as soon as the slurry is set by gelling, the mould being supported during the burning of the alcohol in such a way that there is free circulation around all surfaces of the mould so that ignition and burning of the alcohol occurs evenly from all surfaces. This type of process is described in British Patent Specification No. 716,394. The moulds, part-moulds or cores are suitable for the casting of metals and/or alloys.

Experiments with Zirconium Formate Solution

Zirconium formate is available as an aqueous solution containing approximately 22% ZrO₂. The following conditions were found to produce rigid coherent gels from this solution.

    ______________________________________                                         Using solution of 40g magnesium acetate crystals (4H.sub.2 O)                  in 100ml zirconium formate solution                                            10ml solution + 5ml of                                                                         triethanolamine                                                2 volumes - Tgel                                                                solution comprising                                                                           water                                                          1 volume  45 sec                                                                               640P I.M.S.                                                    1 volume                                                                       10ml solution + 4ml solution                                                    solution comprising                                                                           triethanolamine                                                1 volume - Tgel                                                                                water                                                          1 volume  30 sec                                                               Using solution of 20g fructose in 100ml zirconium                              formate solution                                                               10ml solution + 4ml solution                                                    solution comprising                                                                           triethanolamine                                                1 volume - Tgel                                                                                water                                                          1 volume between                                                                                            10 and                                                                         15 min.                                           Using solution of 40g fructose in 100ml zirconium                              formate solution, with gelation agent comprising                               triethanolamine - 1 volume; water - 1 volume                                   10ml solution + 3ml gelation agent                                             Tgel 25mins.                                                                   10ml solution + 4ml gelation agent                                             Tgel 25mins.                                                                   10ml solution + 5ml gelation agent                                             Tgel 35secs.                                                                   10ml solution + 6ml gelation agent                                             Tgel 21/2mins. - soft gel                                                      10ml solution + 7ml gelation agent                                             Tgel about 1 hour                                                              Using solution of 40g sorbitol in 100ml zirconium                              formate solution, with gelation agent comprising                               triethanolamine - 1 volume; water - 1 volume                                   10ml solution + 4ml gelation agent                                             Tgel = 10 secs.                                                                10ml solution + 5ml gelation agent                                             Tgel = 10 secs.                                                                10ml solution + 6ml gelation agent                                             Tgel = 10 secs.                                                                Using solution of 20g glycine in 100ml zirconium                               formate solution, with gelation agent comprising                               triethanolamine - 1 volume; water - 1 volume                                   10ml solution + 4ml gelation agent                                             no gel after 17 mins.                                                          10ml solution + 5ml gelation agent                                             Tgel = 1 min. gel which                                                                           was a little soft                                                              became quite tur-                                                              bid on standing                                             10ml solution + 6ml gelation agent                                             Tgel = 25 secs. Turbid                                                                            gel.                                                        ______________________________________                                    

Example XXXIV Use of Steetley Ceramic Powder (Spinel Containing) and Ammonium Zirconium Carbonate (AZC Solution)

A crucible was prepared by mixing 35 ml of AZC solution with 200 g of a refractory aggregate comprising of 2 parts by weight of MCH 200 powder and 4 parts by weight of MCH -14+25 powder. The resulting slurry was poured into a crucible mould, which was being vibrated. The slurry set in about 4 minutes, becoming quite hard after 8 minutes. The object was removed from the mould then air dried and fired at 1580° C. to give a crucible. An alternative refractory aggregate (termed Mix D) is:

    ______________________________________                                         3 parts by weight  MCH-8+25                                                    3 parts by weight  MCH-14+25                                                   1 part by weight   MCH 85                                                      2 parts buy weight MCH 150                                                     2 parts by weight  MCH 200                                                     ______________________________________                                    

A crucible was prepared by mixing 30 ml of AZC solution with 200 g of Mix D. The resulting slurry was poured into a crucible mould which was being vibrated. The slurry had a working time of about 3 minutes. The object was removed from the mould in about 10 minutes, then air dried and fired at 1580° C. to give a crucible.

Experiments Using Steetley Ceramic Powder

The refractory aggregate used was Mix D.

Using Zirconyl Chloride Solution (170 g ZrOC1₂.8H₂ O in 110 ml H₂ O)

200 g Mix D with 30 ml of solution - slurry had 2 minutes working time - strip in 5 minutes. Good green strength. Better results obtained using 200 g Mix D with 15 ml of solution and 15 ml 64 OP I.M.S.

Using Zirconium Formate Solution

Satisfactory crucible made using 200 g Mix D with 30 ml of zirconium formate solution. Removed from mould after 3 minutes.

Using Zirconium Acetate Solution

(i) 200 g Mix D with 30 ml zirconium acetate solution gave 4 minutes working time, remove from mould after 5 minutes.

(ii) 200 g Mix D with 30 ml of solution of 10 g magnesium acetate (4H₂ O) crystals in 100 ml of zirconium acetate solution gave 4 minutes working time, remove from mould after 41/2 minutes.

(iii) 200 g Mix D with 30 ml of solution of 40 g magnesium acetate (4H₂ O) crystals in 100 ml of zirconium acetate solution gave a flexible moulding, still plastic after 12 minutes, remove from mould after 16 minutes.

(iv) 200 g Mix D with 20 ml of solution of 10 g glycine in 100 ml of zirconium acetate solution plus 10 ml 640P I.M.S. gave a maximum of 6 minutes working time, remove from mould in 14 minutes - pliable.

(v) 200 g Mix D with 30 g of solution of 10 g betaine in 100 ml of zirconium acetate solution gave a slurry with a working time of 41/2 minutes, remove from mould in 6 minutes. Good surface finish. Similar results obtained using solution of 20 g betaine in 100 ml of zirconium acetate solution, with or without the addition of 640P I.M.S. Adding 640P I.M.S. gave a longer working time.

(vi) 200 g Mix D with 30 ml of a solution comprising 8 parts by volume of zirconium acetate solution with 2 parts by volume of syrupy ammonium lactate solution gave a slurry with a working time of 11 minutes, remove from mould in 40 minutes. Changing the composition of the solution to 9 parts by volume of zirconium acetate with 1 part by volume of syrupy ammonium lactate solution gave a slurry with a working time of 6 minutes, remove from mould in 10 minutes.

Reference is made to the U.S. Application Ser. No. 561,245 of even date corresponding to U.K. application No. 13834/74. 

We claim:
 1. A method of making a refractory article comprising:(a) preparing a liquid, flowable slurry by combining a refractory powder, an aqueous solution of a zirconium salt which when dissolved in water yields an aqueous solution that is acidic, a gellation-inducing agent, and a gellation-delaying agent; said gellation-inducing agent being selected from the group consisting of aminoalcohols, morpholine, dead burned magnesia powder and powdered magnesia-containing spinels and said gellation-delaying agent being selected from the group consisting of magnesium acetate, magnesium lactate, ammonium lactate, glycine, betaine, fructose and polyhydric alcohols; the amounts of refractory powder, solution of zirconium, salt, gellation-inducing agent and gellation-delaying agent being such that the slurry will set to a coherent state upon standing; (b) pouring the slurry while liquid into a mold; (c) allowing the slurry in the mold to set to form a coherent green shape; and (d) removing the green shape from the mold, drying the green shape and firing the dried green shape to form a sintered refractory article.
 2. The method of claim 1 wherein said zirconium salt is zirconium acetate, said gellation-inducing agent is an ethanolamine and said gellation-delaying agent is magnesium acetate.
 3. The method of claim 2 wherein the gellation-inducing agent is triethanolamine, said slurry further including ammonium chloride.
 4. The method of claim 1 wherein the gellation-inducing agent is triethanolamine and said group of gellation-delaying agents further includes acetic acid and triethanolamine hydrochloride.
 5. The method of claim 1 wherein the zirconium salt is zirconium acetate, the gellation-inducing agent is selected from the group consisting of aminoalcohols and morpholine and the gellation-delaying agent is a compound selected from fructose, glycerol, manitol, sorbitol and ammonium lactate, said slurry further containing magnesium chloride.
 6. The method of claim 1 wherein the zirconium salt is zirconium acetate, the gellation-delaying agent is magnesium acetate and the gellation-inducing agent is magnesia or a magnesia-containing spinel, the solution of zirconium acetate further containing an alkali metal borate dissolved therein.
 7. The method of claim 1 wherein the zirconium salt is zirconium acetate, the gellation-delaying agent has a further ingredient magnesium chloride dissolved in the zirconium acetate solution and the gellation-inducing agent is a solution of triethanolamine containing dissolved therein as a further ingredient, a compound selected from the group consisting of ammonium chloride, acetic acid and triethanolamine hydrochloride. 